Biomedical Materials Roger Narayan Editor

Biomedical Materials Roger Narayan Editor Biomedical Materials 123 Editor Roger Narayan Department of Biomedical Engineering University of North Carolina, Chapel Hill 152 MacNider Hall Chapel Hill, NC 27599-1175 USA roger [email protected] ISBN 978-0-387-84871-6 e-ISBN 978-0-387-84872-3 DOI 10.1007/978-0-387-84872-3 Library of Congress Control Number: 2008939136 c Springer Science+Business Media, LLC 2009 All rights reserved. This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights. Printed on acid-free paper springer.com A Historical Perspective on the Development of Biomedical Materials There have been enormous strides in the development of novel biomedical materials over the past three decades. A biomedical material (also known as a biomaterial) is a polymer, metal, ceramic, or natural material that provides structure and/or function to an implantable medical device. In one generation, a large number of biodegradable polymers, bioactive ceramics, and wear-resistant metal alloys have made their way from research laboratories into widely-used medical devices. This heavy flurry of recent progress by materials scientists has partially overshadowed the efforts of surgeons, who previously led research efforts to develop biomedical materials. Until the 1960’s, surgeons were at the forefront of efforts to find new materials for use in medical prostheses. Surgeons were driven by their clinical duties to improve the treatment of those suffering from congenital malformations, trauma, or disease. These surgeon-scientists attempted to alleviate patient suffering using “off-the-shelf” materials, which were developed for nonmedical applications. This brief historical perspective describes some initial efforts to develop novel biomedical materials. Bronze or copper have been used for thousands of years to repair fractured bones. However, use of bronze or copper was limited due to copper accumulation in the eyes, liver, brain, and other body tissues. Two developments in the late nineteenth century accelerated the use of synthetic materials in the human body. The development of the X-ray revealed that conventional external treatments were insufficient and stimulated the development of internal fixation procedures. In addition, broad acceptance of Lister’s antiseptic procedures allowed for internal treatment of medical conditions with minimal risk of infection. Lister himself used antiseptic procedure to successfully suture fractured patellae with silver wire in 1885. Themistocles Gluck described replacement of both the acetabulum (pelvis) and femur (hip bone) using carved ivory at the 10th International Medical Congress in 1890; however, bone resorption and concomitant infection eventually caused these prostheses to fail. Neither acceptable materials nor designs were available at the time to fabricate medical devices. Surgeons made several advances in biomedical materials development in the early- to mid- twentieth century. At the turn of the century, many European surgeons were experimenting with celluloid, rubber, magnesium, zinc, and other materials. In 1924, A. A. Zierold described an animal study on the interaction between bone v vi A Historical Perspective on the Development of Biomedical Materials and several metals, including aluminum, aluminum alloy, copper, low carbon steel, cobalt-chromium alloy, gold, iron, lead, magnesium, nickel, silver, and zinc. X-ray and histological sections of canine bone-material interface revealed that gold, silver, stellite, lead, and aluminum were encapsulated by tissue and were well-tolerated by the animals. Venable, Stuck, and Beach demonstrated the electrolysis of implanted biomedical materials in a 1937 study. They placed aluminum, brass, carbon, cobalt- chromium alloy, copper, galvanized iron, gold, lead, magnesium, nickel, silver, stainless steel, vanadium steel, and zinc in bones of experimental animals. Their bio- chemical, radiographic and clinical findings demonstrated that ion transfer between different metals in the body occurred in accordance with electromotive force. Their work also demonstrated that cobalt-chromium alloy was essentially nonelectrolytic; this material has remained a mainstay medical alloy to the present day. The orthopedic surgeon Sir John Charnley, made several significant advances in the field of biomedical materials, including (a) the introduction of the metal-ultra high molecular weight polyethylene bearing couple; (b) the use of poly (methyl methacrylate) for fixation; (c) the reduction of postoperative sepsis due to the use of laminar flow air-handling systems and prophylactic antibiotics; and (d) the place- ment of antibiotics in bone cement. In the 1950’s, Charnley discovered that natural joints exhibit boundary lubrication. He then attempted to find a synthetic material with similarly low frictional properties. His first choice for an acetabular cup material, polytetrafluoroethylene, demonstrated poor wear properties. Unfortunately, this issue only became evident after a large clinical trial involving polytetrafluoroethylene implants had begun. More than three hundred polytetrafluoroethylene implant surgeries had to be revised due to poor wear properties, necrosis, and implant loosening. Charnley’s laboratory assistant subsequently examined ultra high molecular weight polyethylene, which had found use in mechanical looms. Charn- ley noted that: (a) polyethylene had better wear characteristics than polytetrafluoroethylene; and (b) polyethylene was capable of being lubricated by synovial fluid. The use of novel materials and surgical procedures revolutionized the practice of joint replacement surgery and raised the success rate of this procedure to an ex- ceptionally high level (>90%). Charnley’s total hip replacement is considered the gold standard for joint replacement; few changes have been made to this prosthesis design in the past forty years. However, the Charnley prosthesis does have several disadvantages. One is an unacceptable rate of wear (about 200 μm/year). Metallic and, more commonly, polymeric wear particles cause a severe foreign- body reaction in the tissues that surround the prosthesis, which can lead to implant loosening. The modern field of biomedical materials science owes a great deal to these pi- oneering individuals, who utilized existing knowledge at the interface of materials science and biology in order to improve the quality of life for others. In a similar manner, current-day biomedical materials researchers who work on porous coatings, bulk metallic glasses, artificial tissues, and nanostructured biomedical materials are utilizing modern concepts at the interface of materials science and biology in order to further knowledge in this rapidly developing area. A Historical Perspective on the Development of Biomedical Materials vii The goal of this book is to address several core topics in biomedical materials, including the fundamental properties of the materials used in medicine and dentistry; the interaction between materials and living tissues; leading applications of polymers, metals, and ceramics in medicine; and novel developments in biomedical materials. Homework problems and other material for each chapter can be found at the website http://springer.com/978-0-387-84871-6. We hope that this work will spur productive discussions and interactions among the many groups involved in the development and use of biomedical materials, including biomedical materials researchers, biologists, medical device manufacturers, and medical professionals. Finally, we would like to thank Elaine Tham, Lauren Danahy, and the staff at Springer Science+Business for making this book possible. Chapel Hill, North Carolina Roger Narayan Contents Part I The Fundamental Properties of the Materials Used in Medicine and Dentistry 1 Ceramics and Glasses ........................................... 3 Irene G. Turner 1.1 Introduction .............................................. 3 1.2 WhatIsaCeramic?........................................ 4 1.3 CeramicProcessing........................................ 5 1.4 PowderProcessing......................................... 5 1.5 DeformationandFracture................................... 7 1.6 Transformation Toughening . ............................ 9 1.7 PressurelessSintering...................................... 10 1.8 IsostaticPressing.......................................... 10 1.9 Liquid Phase Sintering . ................................... 12 1.10 TapeCasting.............................................. 13 1.11 CostsofPowderProcessing................................. 13 1.12 PorousCeramics.......................................... 13 1.12.1 BurPS ........................................... 13 1.12.2 FoamedSlips ..................................... 14 1.12.3 ReticulatedFoams................................. 14 1.13 MeasurementofPorosityinPorousCeramics.................. 15

Load more